It was possibly the most intriguing whodunit in the history of Australian crime. Not any more.

But there are many true crime aficionados who will be less than happy with the final solution provided by documentary filmmaker Peter Butt in his Who Killed Dr Bogle and Mrs Chandler?, aired on ABC TV last night.

Because, in the final minutes of Butt’s engaging, adequately researched program, it emerges that it was the river wot dunnit.

The Lane Cove River in Sydney, to be exact. It was on its banks that the partially clad bodies of CSIRO scientist Dr Gilbert Bogle, and his lover, Margaret Chandler, were found on New Year’s Day, 1963.

In the 40 years since the discovery, theories for the two deaths have ranged from murder by Margaret’s husband Geoffrey, to poison darts, to an overdose of hallucinogens.

Neither body bore signs of violence nor traces of poison. But both were fastidiously covered in their own neatly folded clothing.

Enter Thomas Milby, a scientist with the unlikely title of the world’s leading expert on hydrogen sulphide deaths.

Milby considered a suspect that investigating police had overlooked – the river. He unearthed tests, carried out on the stretch of water 15 years before the two deaths, which had revealed a strange phenomenon.

The bottom of the river had literally exploded, sending bubbles of highly poisonous gas to the surface, killing thousands of fish and eels in the process.

The cause was chemical pollution pumped into the river from a nearby factory. And at dawn, when the two lovers wandered down to the banks, Milby theorises, a similar explosion had just happened.

The highly toxic hydrogen sulphide gas would have concentrated in the hollow where they lay, quickly overpowering and killing them, leaving scarcely a trace.

Just about the only unusual finding on the two bodies was a strange, purple discolouration of the blood, a typical symptom of hydrogen sulphide poisoning, according to Milby.

And the neatly folded clothing covering the bodies? According to Butt’s documentary the culprit was a puritanical greyhound trainer exercising his dogs in the area.

So shocked was he by his discovery, and so anxious to protect others from stumbling upon half-naked corpses, that he concealed the victims beneath their clothing. And never reported what he had done.

The trainer in question is now dead, and therein lies the vulnerable area of Butt’s theory. Before he died, the man denied his involvement.